The finishing process for high quality textiles such as washcloths generally has been performed manually because of the attention to detail that is required. The edges of a washcloth must be sewn to prevent fraying and to produce a desirable and lasting product. The process is therefore labor-intensive and time-consuming.
In the manual finishing process, each individual washcloth is cut from a strip of material. The material, typically terry cloth, comes in a continuous strip with transverse borders or "cut lines" present in the fabric at equally spaced intervals along the length of the strip. The cut line is generally an area in the cloth without any terry loops or plush material that represents where each individual washcloth is to be cut from the strip.
After each washcloth is cut, an operator maneuvers the washcloth around a sewing head to stitch or over-edge the sides. A high amount of operator skill is required to produce a washcloth with four uniform sides because the dimensions of each side of the material can often vary. Rounded-corner washcloths are particularly difficult to finish because each corner of the washcloth must be rounded in a uniform fashion. UPC labels, cloth loop labels, or single-ply labels also may be added to the edges of the washcloth.
While attempts have been made to automate the washcloth finishing process, these attempts have not been successful with respect to quality control and with respect to production time because of the lack of uniformity in the material. For example, the center of the corner radius of a washcloth should be positioned to an accuracy of less than 0.060 to 0.100 inches. If the dimensions of the washcloth differ by more than this amount in either length or width, as is often the case, the corners will not be properly stitched and the labels will not be properly attached.
Attempts to automate the washcloth finishing process include U.S. Pat. No. 4,685,408 to Frye, disclosing the use of a plate to guide a pre-cut washcloth into a rotating sewing head. Frye, however, simply finishes each washcloth to a standard dimension and thus does not accommodate the dimensional variations of each washcloth. Further, Frye does not have the ability to change the center of rotation at the corners of the washcloth because of the mechanically-fixed rotation. Smaller washcloths generally need smaller corner radii. The use of a rotating sewing head is also disfavored by the industry because of the thrust and lateral loads that are created within the sewing head. The centrifugal forces imparted to the sewing head impair lubricant dispersal and the associated cooling effects such that high maintenance is required.
Other attempts to automate the washcloth finishing process include U.S. Pat. No. 5,018,462 to Brocklehurst. Brocklehurst discloses the maneuvering of a washcloth around a sewing head by the use of a rotating plate controlled by optical sensors. Rotation of the plate is activated by a sensor detecting a corner of the washcloth and continues until the next corner is detected. The desired position for the center of the radius of each corner, however, may not be the same for all four corners of the washcloth. Rather than accommodating the actual dimensions of the entire washcloth, the apparatus of Brocklehurst simply finishes each corner on same axis of rotation.
What is needed therefore is a means for accommodating nonuniform workpieces into an automated finishing system. Without this ability to adapt to the dimensions of each individual washcloth, even minor variations in the raw material can lead to an unsatisfactory product.